The present invention relates to an electrochemical machining method and an electrochemical machining equipment for carrying out micromachining by an electrochemical reaction using a machining electrode in an electrolytic solution in the fields of metal industry, electronic industry and the like, and particularly to an electrochemical machining method and an electrochemical machining equipment carrying out electrochemical machining while maintaining a predetermined distance between a machining electrode and a work piece with a reference of a zero contact reference position nullifying the distance between the machining electrode and the work piece.
There has conventionally been known a method of carrying out micromachining of a work piece by an electrochemical reaction using a stylus having a fine tip in a solution in the fields of metal industry, electronic industry and the like (Japanese Unexamined Patent Publication No. JP-A-06-299390).
According to the method, it is necessary to shorten a distance between a machining electrode and a work piece in order to promote machining accuracy. It is necessary to make the distance between a machining electrode and a work piece fall in a range of 10 .mu.m (micrometer) or less when machining is carried out with an accuracy of a micrometer order and it is difficult to control such a very small distance with high accuracy. The reason is that 1. a machining electrode and a work piece are present in a solution, 2. although there is a technology capable of measuring with high accuracy a change in a relative distance as in a laser displacement meter or the like, according to such a measuring method, the absolute distance cannot be measured unless the point of the distance cannot be specified, and so on. Hence, a method where a point at which a machining electrode and a work piece are brought into contact with each other is measured by some method, the point is set to the original point and the distance is measured by using a separate highly accurate scale, is conceivable. As a method of detecting the contact, 1. a method of measuring a resistance value between a machining electrode and a work piece and the like are conceivable. Further, as another method of measuring a very small distance, 2. measuring an electrostatic capacity between a machining electrode and a work piece, 3. measuring a tunnel current and the like are conceivable. However, according to these methods, the following problems exist.
Accordingly to the first method, there are cases where the surface of the machining electrode or the work piece is covered with a thin oxide film or the like and the contact may not be detected unless the machining electrode is pushed to the work piece with some degree of force. A diameter of a distal end of the machining electrode is several hundreds .mu.m or less to promote machining accuracy and therefore, there poses a technical problem where the distal end is crushed when it is pushed hard.
Further, it is necessary to apply a voltage between the machining electrode and the work piece to measure the resistance value and when the reactivity of the work piece is high in an electrolyte solution, there also poses a technical problem where when a voltage larger than a standard electrode potential difference is applied between the machining electrode and the work piece, an electrochemical reaction is caused by the voltage and machining is performed.
Further, according to the second method, when the kind or concentration of used solution is changed, the dielectric constant is also changed and therefore, it is necessary to previously measure a relationship between the distance between electrodes and the electrostatic capacity. Further, there poses a technical problem where in measuring the electrostatic capacity in a solution, a measured value is liable to suffer influence of noise which is caused by convection of the solution or the like.
Further, according to the third method, although the method is ideal for detecting the original point since the method is performed strictly in a noncontact state, a diameter of a distal end of the machining electrode needs to be made very small for detecting tunnel current in a solution in order to exclude influence of Faraday current, charge current to an electric double layer and the like and when the diameter of the distal end of the machining electrode is reduced to several tens through several hundreds .mu.m (micrometer) in order to promote machining speed, there poses a technical problem where detection of tunnel current in a solution is very difficult.